eratic speedo

[chkmates12]

Been having this problem with my truck for quite sometime now, after it died out of nowhere a few years back. Floor it and it revs high and slowly picks up speed. It acts like it doesn't know what gear to be in. The speedometer is floating around after I reach about 20mph and will waver 10 - 20 mph above and under what I'm driving, at around 70 it will drop down to 20 and cause me to downshift hard. The motor is the 351 with the E4OD behind it.

The abs light was on and o/d light was blinking till I replaced the sensor on my differential, it shifted a little better at first but gradually went back to how it was acting.The wiring for the sensor isn't corroded.

I've heard that the PSOM could cause all the problems here, that that solder points weren't very well and could cause components to come lose, so my question is, is there a way to test if this is my problem and would there be a cheap way to fix it?

[Steve83]

Originally Posted by chkmates12

Been having this problem with my truck...

...which is WHAT??? Click this, read the WHOLE caption, and follow the instructions:

[miesk5]

yo chkmates12,
WELCOME!

Today is a good day for me to guess what year range you have and if it is a Bronco; Since you mentioned E4OD along w/OD light and PSOM;
92-96, Correct?

If so,
Before buying any parts;
This problem could be caused by a # of thangs;

bad vehicle speed sensor (VSS) (also called ABS,, DSS sensor) on da 8.8 (rear differential)/ or Connector/corroded Terminals/wires inside connector;
or cruddy/damaged tone ring in the 8.8.
bad wiring/shorts /connectors from VSS at firewall, at 4WABS Module and /or at PSOM and then onto the PCM
bad 4WABS Module - It is located below ws wiper fluid/coolant recovery tank. So, the connector can be corroded by leaking fluid
bad PSOM (Speedo)


Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19
The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.
Run it around to heat the engine up and shift thru all gears incl Reverse. Then turn off all accessories/lights, etc.

Make sure A/C is off and transmission is in Park (automatic) or in Neutral for a Manual & release clutch.

Do Key On Engine Off (KOEO) portion first.

Look Codes up in my broncolinks.com site using the new Search function.

And Post em here according to:
KOEO
&
KOER

More tests and info in my reply #8 @ http://fullsizebronco.com/forum/showthread.php?t=201477

And do what Steve suggested and soon in your profile, include your year, engine, trans, Xfer case & locking hub type (auto or manual) and any major mods such as body or suspension lift, etc. or in any question post. You'll get more accurate replies

[Kingfish999]

pull the diff cover and check the fluid. check the toner ring. chekc for any damage whatsoever while your under there.